PretoriaData.m from Nectar, humidity, honey bees (Apis mellifera) and varroa in summer: a theoretical thermofluid analysis of the fate of water vapour from honey ripening and its implications on the control of Varroa destructor

This theoretical thermofluid analysis investigates the relationships between honey production rate, nectar concentration and the parameters of entrance size, nest thermal conductance, brood nest humidity and the temperatures needed for nectar to honey conversion. It quantifies and shows that nest humidity is positively related to the amount, and water content of the nectar being desiccated into honey and negatively with respect to nest thermal conductance and entrance size. It is highly likely that honeybees, in temperate climates and in their natural home, with much smaller thermal conductance and entrance, can achieve higher humidities more easily and more frequently than in man-made hives. As a consequence, it is possible that Varroa destructor, a parasite implicated in the spread of pathogenic viruses and colony collapse, which loses fecundity at absolute humidities of 4.3 kPa (approx. 30 gm−3) and above, is impacted by the more frequent occurrence of higher humidities in these low conductance, small entrance nests. This study provides the theoretical basis for new avenues of research into the control of varroa, via the modification of beekeeping practices to help maintain higher hive humidities.

本理论热流体分析探究了蜂蜜产率、花蜜浓度与蜂箱入口尺寸、蜂巢热传导率、育幼巢湿度以及花蜜转化为蜂蜜所需温度之间的关联。本研究量化并揭示：蜂巢湿度与待脱水制备蜂蜜的花蜜总量及含水量呈正相关，而与蜂巢热传导率及入口尺寸呈负相关。可以推测，在温带气候下的自然蜂巢中，由于其热传导率与入口尺寸均更小，蜜蜂相较于人工养殖蜂箱，能够更轻松且更频繁地维持更高的巢内湿度。据此，寄生性螨类狄斯瓦螨（Varroa destructor）——作为致病性病毒传播与蜂群崩溃的关联媒介——其繁殖能力在绝对湿度达到4.3 kPa（约30 g·m⁻³）及以上时会下降；而这类低传导率、小入口的自然蜂巢更频繁出现的高湿度环境，可能会对狄斯瓦螨产生影响。本研究为通过调整养蜂实践以维持更高蜂箱湿度、进而开展狄斯瓦螨防控的新型研究方向提供了理论基础。